A flexible mobile audio processor

C-DSP 6x8

Filling a gap in our growing product line up for mobile audio enthusiasts, The C-DSP 6x8 is an all in one processor with analog and digital inputs.

A tiny powerhouse

nanoSHARC Kit

Our smallest yet most powerfull platform The nanoSHARC kit combines the power of XMOS and Sharc DSP in a perfect combo for OEM/DIY applications

Bare board basics

A DIYer at heart? So are we. Many of our products are available as bare boards, along with a range of accessory boards for I/O. Fit them into existing equipment, or combine with other boards into your own chassis. Build your own dream audio component.

A World of Learning

At miniDSP, we value training and educating our customers above all. Make sure to check out our extensive training material.

USBStreamer Kit

95 USD

PWR-ICE125

295 USD

miniDSP 2x4 HD kit

195 USD

Digital crossovers are one of the key core strengths of the miniDSP range of products. In this app note, we'll provide an overview of digital crossovers and how they differ from passive crossovers and other types of active crossover. With a high degree of flexibility, user-friendly interfaces, and unbeatable value, miniDSP digital crossovers offer the perfect solution for both the DIYer and the loudspeaker/system professional.

A passive crossover uses only components such as resistors, coils (inductors), and capacitors to divide the signal from the power amplifier into different frequency bands for the different drivers — woofer, midrange, tweeter, for example. (The term "passive" refers to a device or circuit that is not able to control electron flow supplied from a power source, like a transistor, tube, or opamp.)

The following diagram shows a typical system configuration, where volume control () is done in the preamp and the passive crossover is located in the loudspeaker cabinet. The diagram shows a second-order two-way crossover, which has relatively gradual cutoff slopes on the woofer and tweeter — more components will be needed for steeper cutoff slopes. Also, more complex speakers, such as a three-way or four-way, will have a lot more components than shown here.

An active crossover, in contrast, divides the frequency band using the line-level signal and is typically positioned between a preamplifier and the power amplifiers. Each loudspeaker driver has its own dedicated channel of amplification, as shown in the diagram below.

Connecting a driver directly to an amplifier channel improves damping factor and gives the amplifier greater "control" over the driver. (A capacitor is often used in series with the tweeter to protect it from possible low-frequency or DC transients, especially at turn-on or turn-off.) The large — often expensive — passive components between the amplifier channels and the speaker drivers are no longer needed. This advantage is even greater for three-way and 4-way speakers, as they need larger component values for lower crossover frequencies.

Until recently, most active crossovers were implemented with analog circuitry, typically using op-amps to realize specific types of circuit topologies. Switches or plugin-modules select different crossover frequencies. This type of active crossover is limited by the fact that each filter has to be realized with a physical circuit. For example, making the crossover slope steeper would require additional analog circuitry - not easy once a unit is in the field.

With modern DSP (digital signal processing) technology, active crossovers can be implemented entirely with digital computation. This means that the audio processing can be changed much more easily, without any hardware changes. The amount of audio processing is limited only by the DSP power available. Digital crossovers also support direct digital input from a digital source, such as a computer. The following diagram shows a typical system configuration, where volume control can be done digitally either in the source or in the crossover itself. (Note that digital crossovers still support analog input as in the diagram above.)

Digital crossovers from miniDSP incorporate many additional functions, enabled by flexible onboard DSP and our friendly user interfaces. We have also put together an extensive library of application notes to help you make the most of these features!

Flexibility. miniDSP crossovers span the range from simple two-way up to complex four-way (or even five-way) configurations. The following app notes explain how it's done:

In addition to the active crossover itself, you will need loudspeaker boxes with drivers. You can either build a set from scratch, or convert an existing loudspeaker into an active speaker by removing the passive crossover.

You will need sufficient channels of amplification: one per loudspeaker driver. You may even have enough stereo amplifiers available already. Otherwise, multi-channel amps intended for home theater applications will work well and are available at very reasonable prices, and if you have a DIY inclination then Class D power amplifier circuit boards with two, four, and even six channels are also available. Or, our PWR-ICE series of plate amplifiers might be a perfect match for your project.

Finally, you will need to be willing to learn! Mastering active crossovers is an adventure, and we're delighted to be part of it. Please register and join in on our forum to join other like-minded folks building active speaker systems.